Question: $\left(-9x - 7\right)\left(-x - 10\right) = \ ?$
$= -9x \cdot \left(-x - 10\right) - 7 \cdot \left(-x - 10\right)$ $= \left( -9x \cdot -x \right) + \left( -9x \cdot -10 \right) + \left( -7 \cdot -x \right) + \left( -7 \cdot -10 \right)$ $= 9x^2 + \left( -9x \cdot -10 \right) + \left( -7 \cdot -x \right) + \left( -7 \cdot -10 \right)$ $= 9x^2 + \left( 90x + 7x \right) + \left( -7 \cdot -10 \right)$ $= 9x^2 + 97x + \left( -7 \cdot -10 \right)$ $= 9x^2 + 97x + 70$